In the 1983 case Nix v. Williams, the U.S. Supreme Court ruled on a matter of evidence obtained through an illegal police interrogation. Robert Williams had been arrested for murder and his lawyer instructed police not to question him during transport; however, one officer did so anyway, leading Williams to reveal where he'd hidden the victim's body. The court initially suppressed this evidence due to it being unlawfully obtained (the "fruit of the poisonous tree" doctrine). However, upon appeal by Warden Nix in what is known as 'inevitable discovery rule', it was argued that authorities were already conducting a search and would have found the body regardless of William’s admission. The Supreme Court agreed with this argument in a 7-2 decision stating that if illegally obtained evidence could be proven beyond reasonable doubt that it would eventually have been discovered legally then it can be admitted into court proceedings without violating Fourth Amendment rights against unreasonable searches or seizures.

In the dissenting opinion for Nix v. Williams, Justice Brennan argued that the majority's decision undermined the constitutional rights of defendants by allowing evidence obtained through unconstitutional means to be used in court if it could have been discovered inevitably through legal methods. He contended that this "inevitable discovery" exception to the exclusionary rule would encourage law enforcement officers to disregard suspects' Miranda rights since any evidence they found illegally might still be admissible in court. Furthermore, he criticized how difficult it would be for courts to determine whether or not certain pieces of evidence would have been inevitably discovered and predicted that this ambiguity could lead to further violations of defendants' rights.